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Black Box Explains...Augmented Category 6 (CAT6A).


Augmented Category 6 (CAT6a)–Class Ea was ratified in February 2008. This standard calls for 10-Gigabit Ethernet data transmission over a 4-pair copper cabling system up to 100 meters. CAT6a extends... more/see it nowCAT6 electrical specifications from 250 MHz to 500 MHz. It introduces the ANEXT requirement. It also replaces the term Equal Level Far-End Crosstalk (ELFEXT) with Attenuation to Crosstalk Ratio, Far-End (ACRF) to mesh with ISO terminology. CAT6a provides improved insertion loss over CAT6. It is a good choice for noisy environments with lots of EMI. CAT6a is also well-suited for use with PoE+.

CAT6a UTP cable is significantly larger than CAT6 cable. It features larger conductors, usually 22 AWG, and is designed with more space between the pairs to minimize ANEXT. The outside diameter of CAT6a cable averages 0.29–0.35" compared to 0.21–0.24" for CAT6 cable. This reduces number of cables you can fit in a conduit. At a 40% fill ratio, you can run three CAT6a cables in a 3/4" conduit vs. five CAT6 cables.

There are two types of CAT6a cable, UTP and F/UTP.

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Black Box Explains…Component vs. channel testing.

When using a Category 6 system, the full specification includes the testing of each part individually and in an end-to-end-channel. Because CAT6 is an open standard, products from different vendors... more/see it nowshould work together.

Channel testing includes patch cable, bulk cable, jacks, patch panels, etc. These tests cover a number of measurements, including: attenuation, NEXT, PS-NEXT, EL-FEXT, ACR, PS-ACR, EL-FEXT, PS-ELFEXT, and Return Loss. Products that are tested together should work together as specified. In theory, products from all manufacturers are interchangeable. But, if products from different manufacturers are inserted in a channel, end-to-end CAT6 performance may be compromised.

Component testing, on the other hand, is much stricter even though only two characteristics are measured: crosstalk and return loss. Although all CAT6 products should be interchangeable, products labeled as component are guaranteed to perform to a CAT6 level in a channel with products from different manufacturers.

For more information on cable, channel, and component specs, see below.

Buyer’s Guide: CAT5e vs. CAT6 Cable

Standard — CAT5e: TIA-568-B.2; CAT6: TIA-568-B.2-1

Frequency — CAT5e: 100 MHz; CAT6: 250 MHz

Attenuation (maximum at 100 MHz) —
Cable: CAT5e: 22 dB; CAT6: 19.8 dB
Connector: CAT5e: 0.4 dB; CAT6: 0.2 dB
Channel: CAT5e: 24.0 dB; CAT6: 21.3 dB

NEXT (minimum at 100 MHz) —
Cable: CAT5e: 35.3 dB; CAT6: 44.3 dB
Connector: CAT5e: 43.0 dB; CAT6: 54.0 dB
Channel: CAT5e: 30.1 dB; CAT6: 39.9 dB

PS-NEXT (minimum at 100 MHz) — 32.3 dB 42.3 dB

EL-FEXT (minimum at 100 MHz) —
Cable: CAT5e: 23.8 dB; CAT6: 27.8 dB
Connector: CAT5e: 35.1 dB; CAT6: 43.1 dB
Channel: CAT5e: 17.4 dB; CAT6: 23.3 dB

PS-ELFEXT (minimum at 100 MHz) — CAT5e: 20.8 dB; CAT6: 24.8 dB

Return Loss (minimum at 100 MHz) —
Cable: CAT5e: 20.1 dB; CAT6: 20.1 dB
Connector: CAT5e: 20.0 dB: CAT6: 24.0 dB
Channel: CAT5e: 10.0 dB; CAT6: 12.0 dB

Characteristic Impedance — Both: 100 ohms ± 15%

Delay Skew (maximum per 100 m) — Both: 45 ns

NOTE: In Attenuation testing, the lower the number, the better. In NEXT, EL-FEXT, and Return Loss testing, the higher the number, the better. collapse


Black Box Explains…OM3 and OM4.

There are different categories of graded-index multimode fiber optic cable. The ISO/IEC 11801 Ed 2.1:2009 standard specifies categories OM1, OM2, and OM3. The TIA/EIA recognizes OM1, OM2, OM3, and OM4.... more/see it nowThe TIA/EIA ratified OM4 in August 2009 (TIA/EIA 492-AAAD). The IEEE ratified OM4 (802.ba) in June 2010.

OM1 specifies 62.5-micron cable and OM2 specifies 50-micron cable. These are commonly used in premises applications supporting Ethernet rates of 10 Mbps to 1 Gbps. They are also typically used with LED transmitters. OM1 and OM2 cable are not suitable though for today's higher-speed networks.

OM3 and OM4 are both laser-optimized multimode fiber (LOMMF) and were developed to accommodate faster networks such as 10, 40, and 100 Gbps. Both are designed for use with 850-nm VCSELS (vertical-cavity surface-emitting lasers) and have aqua sheaths.

OM3 specifies an 850-nm laser-optimized 50-micron cable with a effective modal bandwidth (EMB) of 2000 MHz/km. It can support 10-Gbps link distances up to 300 meters. OM4 specifies a high-bandwidth 850-nm laser-optimized 50-micron cable an effective modal bandwidth of 4700 MHz/km. It can support 10-Gbps link distances of 550 meters. 100-Gbps distances are 100 meters and 150 meters, respectively. Both rival single-mode fiber in performance while being significantly less expensive to implement.

OM1 and 2 are made with a different process than OM3 and 4. Non-laser-optimized fiber cable is made with a small defect in the core, called an index depression. LED light sources are commonly used with these cables.

OM3 and 4 are manufactured without the center defect. As networks migrated to higher speeds, VCSELS became more commonly used rather than LEDs, which have a maximum modulation rate of 622 Mbps. Because of that, LEDs can’t be turned on and off fast enough to support higher-speed applications. VCSELS provided the speed, but unfortunately when used with older OM1 and 2 cables, required mode-conditioning launch cables. Thus manufacturers changed the production process to eliminate the center defect and enable OM3 and OM4 cables to be used directly with the VCSELS. OM3/OM4 Comparison
850 nm High Performance EMB (MHz/km)

OM3: 2000

OM4: 4700


850-nm Ethernet Distance
1-GbE
OM3: 1000 m

OM4: 1000 m


10-GbE
OM3: 300 m

OM4: 550 m


40-GbE
OM3: 100 m

OM4: 150 m


100-GbE
OM3: 100 m

OM4: 150 m

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Black Box Explains...Fiber optic cable construction.

Fiber optic cable consists of a core, cladding, coating, strengthening fibers, and cable jacket.

Core
This is the physical medium that transports optical data signals from an attached light source to... more/see it nowa receiving device. The core is a single continuous strand of glass or plastic that’s measured (in microns) by the size of its outer diameter. The larger the core, the more light the cable can carry.

All fiber optic cable is sized according to its core’s outer diameter.

The three multimode sizes most commonly available are 50, 62.5, and 100 microns. Single-mode cores are generally less than 9 microns.

Cladding
This is a thin layer that surrounds the fiber core and serves as a boundary that contains the light waves and causes the refraction, enabling data to travel throughout the length of the fiber segment.

Coating
This is a layer of plastic that surrounds the core and cladding to reinforce the fiber core, help absorb shocks, and provide extra protection against excessive cable bends. These buffer coatings are measured in microns (µ) and can range from 250 to 900 microns.

Strengthening fibers
These components help protect the core against crushing forces and excessive tension during installation.

The materials can range from Kevlar® to wire strands to gel-filled sleeves.

Cable jacket
This is the outer layer of any cable. Most fiber optic cables have an orange jacket, although some types can have black or yellow jackets. collapse


Black Box Explains...Digital Visual Interface (DVI) and other digital display interfaces.

There are three main types of digital video interfaces: P&D, DFP, and DVI. P&D (Plug & Display, also known as EVC), the earliest of these technologies, supports both digital and... more/see it nowanalog RGB connections and is now used primarily on projectors. DFP (Digital Flat-Panel Port) was the first digital-only connector on displays and graphics cards; it’s being phased out.

There are different types of DVI connectors: DVI-D, DVI-I, DVI-A, DFP, and EVC.

DVI-D is a digital-only connector. DVI-I supports both digital and analog RGB connections. Some manufacturers are offering the DVI-I connector type on their products instead of separate analog and digital connectors. DVI-A is used to carry an analog DVI signal to a VGA device, such as a display. DFP, like DVI-D, was an early digital-only connector used on some displays; it’s being phased out. EVC (also known as P&D) is similar to DVI-I only it’s slightly larger in size. It also handles digital and analog connections, and it’s used primarily on projectors.

All these standards are based on transition-minimized differential signaling (TMDS). In a typical single-line digital signal, voltage is raised to a high level and decreased to a low level to create transitions that convey data. TMDS uses a pair of signal wires to minimize the number of transitions needed to transfer data. When one wire goes to a high-voltage state, the other goes to a low-voltage state. This balance increases the data-transfer rate and improves accuracy. collapse


Black Box Explains...10GBASE-T standard.

In June 2006, the IEEE approved the standard for 10 Gigabit/sec Ethernet, or 10GBASE-T (10-GbE). 10-GbE transmission requires a bandwidth of 500 MHz.

The 10-GbE standards.
The cabling industry is developing... more/see it nowtwo different standards that can be used in 10-GbE applications. One is for use with Category 6 (CAT6) cable, and one is for Augmented Category 6 (CAT6a).

Alien Crosstalk.
Before discussing the standards, a definition of Alien Crosstalk is needed.

Alien Crosstalk (ANEXT) is a critical measurement unique to 10-GbE systems. Crosstalk, measured in 10/100/1000BASE-T systems, is the mixing of signals between wire pairs within a cable. Alien Crosstalk is the measurement of the signal coupling between wire pairs in different, adjacent cables.

The amount of ANEXT depends on a number of factors, including the promixity of adjacent cables and connectors, the cable length, cable twist density, and EMI. Patch panels and connecting hardware are also affected by ANEXT.

With ANEXT, the affected cable is called the disturbed or victim cable. The surrounding cables are the disturbers.

10-GbE using CAT6.
The first set of standards defines cabling performance when using Category 6/Class E cabling for 10-GbE applications. The TIA/EIA version will be the Technical Systems Bulletin 155 (TSB 155). ISO/IEC TR 24750 is a technical report to be used for measuring existing Class E systems.

No matter what the cable length is, CAT6 cable must meet 10-GbE electrical and ANEXT specifications up to 500 MHz. However, the CAT6 standard now specifies measurements only to 250 MHz, and it does not have an ANEXT requirement. There is no guarantee CAT6 can support a 10-GbE system. But the TSB provides guidelines for ways to help mitigate ANEXT. One way to lessen or eliminate ANEXT is to use shielded equipment and cables. Another way is to follow installation guidelines, such as using non-adjacent patch panels, separating equipment cords, unbundling horizontal cabling, etc.

10GbE using CAT6a.
The second set of standards will define Augmented Category 6 (CAT6a) and Augmented Class E (Class Ea) cabling. The newer, augmented cabling systems are designed to support 10-GbE over a 100-meter horizontal channel.

The TIA/EIA version is in draft and will be published as ANSI/TIA/EIA-568B.2-AD10. It recognizes both UTP and STP CAT6a systems. It also extends CAT6 electrical parameters such as NEXT, FEXT, return loss, insertion loss, and more to 500 MHz. It specifies near- and far-end Alien Crosstalk (ANEXT, AFEXT) to 500 MHz. It also goes beyond IEEE 802.3an by establishing the electrical requirements for the permanent link and cabling components. The ISO Class Ea standard will be published in a new edition of the 11801 standard.

These standards specify requirements for each component in the channel, such as cable and connecting hardware, as well as for the permanent link and the channel. collapse


Black Box Explains...Solid vs. stranded cable.

Solid-conductor cable is designed for backbone and horizontal cable runs. Use it for runs between two wiring closets or from the wiring closet to a wallplate. Solid cable shouldn’t be... more/see it nowbent, flexed, or twisted repeatedly. Its attenuation is lower than that of stranded-conductor cable.

Stranded cable is for use in shorter runs between network interface cards (NICs) and wallplates or between concentrators and patch panels, hubs, and other rackmounted equipment. Stranded-conductor cable is much more flexible than solid-core cable. However, attenuation is higher in stranded-conductor cable, so the total length of stranded cable in your system should be kept to a minimum to reduce signal degradation. collapse


Black Box Explains...SCSI-1, SCSI-2, SCSI-3, and SCSI-5.

There are standards…and there are standards applied in real-world applications. This Black Box Explains illustrates how SCSI is interpreted by many SCSI manufacturers. Think of these as common SCSI connector... more/see it nowtypes, not as firm SCSI specifications. Notice, for instance, there’s a SCSI-5, which isn’t listed among the other approved and proposed specifications. However, for advanced SCSI multiport applications, SCSI-5 is often the connector of choice.

SCSI-1
Supports transfer rates up to 5 MBps and seven SCSI devices on an 8-bit bus. The most common connector is the Centronics® 50 or a DB50. A Micro Ribbon 50 is also used for internal connections. SCSI-1 equipment, such as controllers, can also have Burndy 60 or 68 connectors.

SCSI-2
SCSI-2 introduced optional 16- and 32-bit buses called “Wide SCSI.“ Transfer rate is normally 10 MBps but SCSI-2 can go up to 40 MBps with Wide and Fast SCSI. SCSI-2 usually features a Micro D 50-pin connector with thumbclips. It’s also known as Mini 50 or Micro DB50. A Micro Ribbon 60 connector may also be used for internal connections.

SCSI-3
Found in many high-end systems, SCSI-3 commonly uses a Micro D 68-pin connector with thumbscrews. It’s also known as Mini 68. The most common bus width is 16 bits with transfer rates of 20 MBps.

SCSI-5
SCSI-5 is also called a Very High-Density Connector Interface (VHDCI) or 0.8-mm connector. It’s similar to the SCSI-3 MD68 connector in that it has 68 pins, but it has a much smaller footprint. SCSI-5 is designed for SCSI-5, next-generation SCSI connections. Manufacturers are integrating this 0.8-mm design into controller cards. It’s also the connector of choice for advanced SCSI multiport applications. Up to four channels can be accommodated in one card slot. Connections are easier where space is limited. collapse


Black Box Explains...Ceramic and composite ferrules.

Cables manufactured with ceramic ferrules are ideal for mission-critical applications or connections that are changed frequently. These cables are high quality and typically have a very long life. Ceramic ferrules... more/see it noware more precisely molded and fit closer to the fiber than their composite counterparts, which gives them a lower optical loss.

On the other hand, cables with composite ferrules are ideal for less critical applications or connections that won’t be changed frequently. Composite ferrule cables are characterized by low loss, good quality, and long life. collapse


Black Box Explains...10-GbE, CAT6A, and ANEXT.

The IEEE released the 802.3an 10GBASE-T standard in June 2006. This standard specifies 10-Gbps data transmission over four-pair copper cabling. 10-Gigabit Ethernet (10-GbE) transmission includes up to 37 meters of... more/see it nowCAT6 cable (with installation mitigation techniques), 100 meters of Augmented Category 6 (CAT6A) UTP or F/UTP cable or 100 meters of S/FTP CAT7/Class F cable.

CAT6A is the ANSI/TIA 10-Gigabit Ethernet (10-GbE) over copper standard. Its requirements are covered in ANSI/TIA-568-C.2 (Balanced Twisted-Pair Communications Cabling and Components Standard) published in August 2009. It defines 10-Gigabit data transmission over a 4-connector twisted-pair CAT6A copper cable for a distance of 100 meters.

Category 6A cabling is designed to support next-generation applications, including the transfer of large amounts of data at high speeds, up to 10 Gbps. CAT6A extends electrical specifications to 500 MHz from 250 MHz for CAT6 cabling. CAT6A cables are fully backward compatible with previous categories, including CAT6 and 5e. Category 6A is also designed to support bundled cable installations up to 100 meters and PoE+ low-power implementations. The standard includes the performance parameter, Alien Crosstalk (ANEXT). Because of its higher performance transmission speeds and higher MHz rating, CAT6A cable needs to be tested for external noise outside the cable, which wasn’t a concern with previous cabling categories. CAT6A UTP also has a much larger diameter than previous cables.

Alien crosstalk (ANEXT) is a critical and unique measurement in 10-GbE systems. Crosstalk, measured in 10/100/1000BASE-T systems, is the mixing of signals between wire pairs within a cable. Alien Crosstalk, in 10-GbE systems, is the measurement of the unwanted signal coupling between wire pairs in different and adjacent cables or from one balanced twisted-pair component, channel, or permanent link to another.

The amount of ANEXT depends on a number of factors, including the type of cable, cable jacket, cable length, cable twist density, proximity of adjacent cables, and connectors, and EMI. Patch panels and connecting hardware are also affected by ANEXT.

With Alien Crosstalk, the affected cable is called the victim cable. The surrounding cables are the disturber cables.

There are a number of ways to mitigate the effects of ANEXT in CAT6A runs. According to the standards, ANEXT can be improved by laying CAT6A UTP cable loosely in pathways and raceways with space between the cables. This contrasts to the tightly bundled runs of CAT6/5e cable that we are used to. The tight bundles present a worst-case scenario of six cables around one, thus the center cable would be adversely affected by ANEXT. CAT6A UTP cable needs to be tested for ANEXT. This is a complex and time-consuming process in which all possible wire-pair combinations need to be tested for ANEXT and far-end ANEXT. It can take 50 minutes to test one link in a bundle of 24 CAT 6A UTP cables.

To virtually eliminate the problem of ANEXT, you can use CAT6A F/UTP cable. The F indicates an outer foil shield encasing four unshielded twisted pairs. This cable is also a good choice when security is an issue because it doesn’t emit signals. In addition, CAT6A F/UTP cable works well in noisy environments with a lot of EMI/RFI.

Installation of CAT6A F/UTP is simpler, too, because the cable features a smaller outside diameter than CAT6A UTP. Its construction makes it easier to pull and more resilient. The cable also has a smaller diameter so you can run more cables in a conduit or pathway, and have greater patch panel port density.

For more information, see the CAT6A F/UTP vs. UTP: What You Need to Know white paper in the Resources section at blackbox.com. collapse

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